Electronic devices for high-speed telecommunication and networking applications are typically housed in a metal chassis. Power is typically routed to the chassis by input power cables that are connected to a circuit board located along the backside of the chassis. This circuit board is commonly referred to as a backplane circuit board. The input power cables may, however, introduce unwanted noise and other transients into the chassis. Moreover, electromagnetic emissions generated within the chassis may exit the chassis and may propagate along the input power cables outside of the chassis.
To overcome these problems, a power line filter (i.e., electromagnetic interference/radio frequency interference filter) is typically mounted within the chassis to provide filtered power to the chassis. These filters are typically housed in a relatively large metal box-like housing having input terminals or lugs which extend through a side wall, and output cables that extend through the opposite side wall. Standard electrical capacitors are mounted within the box-like housing. The input terminals are operatively connected to one end of the capacitors, and the output cables are operatively connected to the other end of the capacitors.
Although the input terminals of a conventional filter may extend outside of the chassis, the box-like housing of the filter is typically positioned within the chassis near the top of the chassis. The input power cables to the chassis are typically attached directly to the input terminals of the filter. The output cables leading from the filter are then attached to a backplane circuit board to supply filtered power to the electronic components mounted within the chassis.
There are several disadvantages to these conventional power filters including their relatively large size. Electronic chassis typically have strict dimensional requirements, and the large size of conventional filters greatly reduces the amount space in the chassis that could otherwise be used for other various electronic functions. In addition, despite their large size, conventional filters typically are not very efficient in that they do not optimum filtering over a high frequency range with low impedance.
Moreover, mounting the housing of conventional filters within the chassis blocks the airflow through the chassis, which may result in the overheating of the various electronic components within the chassis. Also, mounting conventional filters within the chassis and routing their output cables to the backplane circuit board is a labor intensive and time consuming process that increases the installation time. Finally, there are typically high costs associated with the manufacture of conventional filters due to the number of parts required to construct the filter, and the complexity of the parts.
Accordingly, it would be desirable to have a laminated filter apparatus that overcomes the disadvantages described above, and to provide a simple and cost effective laminated filter for reducing electromagnetic interference.